Hospitalization and prolonged immobilization often lead to the functional decline of vulnerable older persons. Bed rest and inactivity have been shown to accelerate the functional changes that are part of normal aging. This link between inactivity and adverse outcomes is increasingly appreciated by medical professionals, and the mobilization of critically ill patients is an important aspect of patient care. Monitoring and documenting patient activity levels in acute-care settings is generally nonexistent, as is assurance of adequate levels of mobilization. Staff reports from nurses, physical therapists, physicians, and aides, where extant, often lack agreement and documentation consistency. This is particularly true in the context of competing priorities in busy hospital wards and varying levels of staff knowledge and motivation. Manual patient documentation requirements already place a significant burden on health care professionals and limit the time spent with patients. Patient self-reports of activity levels have questionable validity and reliability, especially in settings where delirium and decreased consciousness are common. These factors all manifest a need for automated monitoring of patient activity levels to provide a safety net and to ensure that prophylactic and therapeutic mobilization of patients is performed. Fortunately, noninvasive and affordable technology is available that can obviate the need for health care professionals to manually document patient mobility levels, freeing their time for patient care and education tasks. The proposed wireless Patient/Resident Mobility Tracker (PREEMPT) will provide an effective, accurate, and practicable method for automatically documenting patient mobility, providing the desired activity/posture information that is relevant in both hospital and senior car settings. In particular, the Phase I PREEMPT will be used to track and provide hourly summaries of the following: (1) sedentary time (time spent lying or sitting); (2) upright time (time spent standing or walking); (3) walking time; (4) step count; (5) step cadence (steps per minute); (6) gait speed (m/s or mi/hr); and (7) number of sit-to-stand transitions (number of posture changes from sedentary to upright). Collected data will be transmitted wirelessly to a touch-screen tablet computer in near real time, where the information will be readily accessible by health care professionals for use in patient management. The PREEMPT will not interfere with other patient monitoring or therapeutic treatments, including chest monitors, arm and neck intravenous lines, Foley catheters, back braces, etc. Using swappable monitors and disposable/recyclable cotton bands, the PREEMPT will require minimal maintenance (e.g., cleaning, etc.), as a key objective of this technology is to decrease clinical staff burden. The PREEMPT can also be used to track patient/resident turning in bed to prevent decubitus ulcers, and to provide an alternative to bed/chair alarms for patients at risk for falls to alert nurses when a patient transitions from bed lying to sitting, or from chair sitting to standing. Further, the PREEMPT can be used in research settings; its advantages include its provisions for expanded posture coverage, gait analysis, near-real-time wireless data uploads, and lower cost.